Electrical musical instrument



Sept. 19, 1950 L. E. A. BOURN ELECTRICAL MUSICAL INSTRUMENT 2 Sheets-Sheet 1 Filed Aug. 7, 1947 OUTPUT p 5 E. A. BOURN 2,522,923

' ELECTRICAL MUSICAL INSTRUMENT Filed Aug. 7, 1947 2 Sheets-Sheet 2 i flanfl, l

j 1 .F T F" flab drA/Il 6mm Patented Sept. 19, 1950 ELECTRICAL MUSICAL INSTRUMENT Leslie Edwin Alexander Bourn, Ashford, England Application August 7, 1947, Serial No. 767,206 In Great Britain October 23, 1944 Section 1, Public Law 690, August 8, 1946 Patent expires October 23, 1964 6 Claims.

This invention relates to electrical musical instruments. The object of the invention is the provision of an improved electrical musical instrument which is in general of the organ type, and which will be less complicated than most of those hitherto in use, While providing a considerable range of tone qualities though falling short of full and complete synthesis.

The invention consists broadly of an electrical musical instrument which is in general of the organ type comprising a plurality of generators which generate complex tones and means whereby, by manipulating said generators, tones can be produced either having a substantially complete series of harmonics or having the odd harmonic only.

In order that the invention may be the more clearly understood, an instrument in accordance therewith will now be described, reference being made to the accompanying drawings, wherein:

Figure l is a face view of one of a number of Scanning discs employed in said instrument;

Figure 2 is a face view to an enlarged scale of a portion of a corresponding disc which is scanned by the disc of Figure 1;

Figure 3 is an illustration of the fundamental circuit connections of one of the electrodes of the disc of Figure 2 together with the relevant portions of electrodes of the disc of Figure 1;

Figure 4 is a graphical representation of the electrical impulses generated by the arrangement of Figure 3 under certain conditions;

Figure 5 is a similar representation of the electrical impulses generated by said arrangement of Figure 3 under other conditions;

Figure 6 is a similar representation of the electrical impulses generated by said arrangement of Figure 3 under still other conditions; and

Figure 7 is a more detailed diagram illustrating the output circuits of a group of electrodes.

The instrument illustrated by these figures is an electrostatic instrument of the same general kind as that described in my prior Patent #2,032,044, a number of stationary discs being employed which carry annular wave-form electrodes, and rotary discs being arranged close to the respective stationary discs, which rotary discs carry grid-like electrodes which scan the waveform electrodes as the rotary discs rotate.

In the present arrangement, each stationary disc, as illustrated in Figure 2, instead of carrying electrodes of pure sine wave form, carries electrodes I of a complex wave form comprising fundamental and complete series of harmonics to a high order. Thus, as shown, the wave forms may be simple saw-tooth forms. In practice, there are twelve such discs each with, say, seven concentric annular wave-form electrodes I mounted on one face thereof. In Figure 2, to avoid unnecessary repetition, only five annular electrodes I are shown on the disc, but, as stated, there would in practice be seven. The electrodes I of each disc are such as to give frequencies which double successively from the innermost to the outermost electrode. The electrodes of each of the twelve discs are identical with those of the other discs and the twelve discs are rotated at relative speeds corresponding to the twelve notes of the tempered musical scale. It will thus be seen that the twelve discs correspond to the twelve notes of the tempered musical scale each disc comprising seven octaves of its note.

Each rotary disc, as shown in Figure 1, carries what is essentially two separate and disconnected grids 2 and 3 for scanning the electrodes of the corresponding stationary disc. For clearness the grid 2 is shown in full lines and the grid 3 in dotted lines. Each grid is essentially similar to the grid of my prior Patent #2,032,044 aforesaid and comprises a set of radial members for scanning each annular electrode of the stationary disc. Thus the grid 2 has a set of radial members which are superimposed over the outermost electrode I and are spaced apart a distance equal to the wave length of said outermost electrode. Said grid 2 also has a set of radial members which are superimposed over the next inner electrode I and are spaced apart a distance equal to the wave length of said next inner electrode, and so on to the radial members which are superimposed over the innermost electrode and are spaced apart a distance equal to the wave length of said innermost electrode.

In like manner, the grid 3 has sets of radial members which are superimposed over the respective electrodes I, and are spaced apart a distance equal to the wave length of the electrode over which they are superimposed. As shown, the radial members of each grid are degrees out of phase with those of the other.

Referring now to Figure 3, which illustrates a fragment of one of the electrodes I and corresponding fragments of the grids 2 and 3, and shows the fundamental circuit connections of said electrode and grids, the keying circuits and other refinements being omitted for the sake of simplicity, it will be seen that the grids 2 and 3 I is connected to the control grid of an electronic 3 valve 1, which is provided with the usual resistances and high tension source of supply as shown, and whose output to the loud speaker is indicated at 3.

If one of the tapped points 4 or brought into coincidence with the centre or neutral point 9 of the source only one of the grids 2 and 3 will be polarised relative to the electrode I. In this case, the impulses fed to the valve l and accordingly transmitted to the output 8 will be an exact replica of the wave forms of the electrode I and will accordingly include all the harmonics of the respective tones. These impulses are represented by the simple saw tooth curve shown in Figure 4, being the wave length.

If the tapped points 5 5 are brought in coincidence with each other at a point removed from the neutral point 5, both the grids will be equally polarised relative to the electrode I. The

impulses fed to the valve 7 will accordingly still be an exact replica of the wave forms of the electrode, but the frequency will be doubled and the only effect will be to raise the pitch one octave, the complete set or harmonics still remaining. The impulses are now represented by the curve shown in Figure 5.

If, however, the tapped points 4 and 5 are located an equal distance on opposite sides of the neutral point 5], so that the grids 2 and 3 are polarised in equal and opposite senses with reference to the electrode i, the resulting impulses will be of the square wave form illustrated in Figure 6. The frequency will be the same as in Figure 4 but the harmonic content will comprise the odd harmonics only.

Obviously, by manipulating the tapped points 4 and 5, an indefinite variety of conditions between the extreme conditions above described can be obtained.

It will, of course, be understood that the grids 2 and 3 throughout the whole range of the instrument are all connected to the same tapped points 4 and 5 so that the setting of said points 4 and 5 determines the quality of the notes throughout the musical range. It will also be understood that keys are provided whose operation determines which of the electrodes I shall speak as will hereinafter appear.

Referring now to Figure 7, which illustrates the keying circuits and also the addition of filters for attenuating certain frequency ranges, each of the electrodes i (not shown in Figure 7) is connected to the control grid of its own proper valve 1 so that, according to the potentials applied to the scanning grids 2 and 3, all the valves 1 are receiving signals continuously. Normally the valves are biased to cut-off and are consequently non-amplifying so that no signal is passed to the output. The valves 1 are associated in groups of four or five consecutive notes, and the anodes of each group are paralleled together and are fed through a common anode load resistance or choke it from a suitable anode supply. Each group is connected through a suitable filter network H to an output I2. The output I2 is common to all the groups and supplies a suitable loud speaker.

Describing now the keying circuit, the grid of each valve is connected through the usual grid. resistance 13 and a second resistance M to a source of potential it which is adjusted to be at or beyond the negative grid bias necessary to keep the valves at cut-off. The junction of each resistance i3 and i4 is connected through a resistance l6 to one side of a of key contacts I! which are closed or opened according to whether a corresponding key is depressed or not. The other side of each pair of contacts I! is connected to a common adjustable source of positive potential I8. When a key is depressed, current flows from said source [8 through the corresponding resistances l8 and I4, and the junction point between the resistances l3 and M has its potential raised and therefore the grid of the corresponding valve 1 has its potential raised above cut-01f potential to a potential determined by the value of the setting of the source [8.

Condensers l9 are also provided connected between the aforesaid junction points and some point of fixed potential such as the negative side of the source IS. The function of these condensers is to minimise key thumps.

It will be seen that a blocking condenser 20 is provided between each group of valves and the filter network ll of said group. The values of the components comprising the filter network vary with the part of the musical scale in which they work. The condensers of all the networks are ganged together and may be varied by a suitable control available to the player.

It will be understood that if the filter networks I i are adjusted s0 as to attenuate the upper fre quencies, the tone, whether containing the odd harmonics only or the complete series of harmonics, will sound more fundamental or fiutelike, whereas, if said filters are adjusted so as to attenuate the lower frequencies, the note will sound more raucous.

It will be seen from the above that, by the use of the two sets of scanning grids 2 and 3 and the adjustable filter networks I I, either odd harmonic tones or complete series tones each with considerable range of variety may be obtained.

It will be apparent that the same tonal effects may be obtained by providing only one set of scanning grids on the rotors and pairs of similar annular electrodes l on the stator, the electrodes l of each pair being displaced degrees in phase relatively. In this case, the scanning grids may be connected to control valves which determine which note is to speak, there being a scanning grid for each note, and the pairs of annular electrodes may be connected to be polarised according to the tone required.

Alternatively, the single set of scanning grids could be connected to a point of fixed potential and the wave form electrodes polarised through high value resistance, the wave forms being also connected to the grids of the valves in series with blocking condensers.

A further method of producing either complete or odd series tones at will is to provide Wave forms accordingly, namely, one of say square tapped form or comprising only of odd harmonics and the second of, say, saw-tooth form of double the fundamental frequency of the first wave, i.e., comprising only of even harmonics. These may be connected according to the above described circuits.

The invention is not limited to the use of electronic valves for controlling the outputs of the electrodes. Alternatively, 1;- contacts could be connected. directly in the polarising circuits in the manner described in prior patents Reissue #19,'? 2, and #2132344.

Th s invention is not confined to the use of 180 degree phase displacements only, as useful effects may be produced with other displacements; nor is the invention necessarily associated with electrostatic generators.

Iclaim: g I 1. An electrical musical instrument comprising a multiplicity of wave-form. electrodes, two scanning electrodes for each wave-form electrode, whereby a multiplicity of frequency generators are constituted corresponding to the tone pitches required throughout the range of the instrument, one scanning electrode of every wave-form electrode being electrically connected to one scanning electrode of every other wave-form electrode, and the other scanning electrodes being also electrically connected together, so that the scanning electrodes are electrically connected in two corresponding sets each of which extends throughout the musical range of the instrument, and means for selectively polarising the two sets of scanning electrodes relative to the wave-form electrodes, whereby electrostatically generated frequencies corresponding to the pitches required throughout the musical range of the instrument may have their tone character simultaneously and uniformly varied.

2. An electrical musical instrument comprising a multiplicity of wave-form electrodes each having a wave form corresponding to a substantially complete series of harmonics, two scanning electrodes for each wave-form electrode, each of said two scanning electrodes comprising a set of transverse lines adapted to scan said wave-form electrode, the lines of the two scanning electrodes being out of phase, said waveform electrodes and scanning electrodes forming a multiplicity of frequency generators corresponding to the tone pitches required throughout the range of the instrument, one scanning electrode of every wave-form electrode being electrically connected to one scanning electrode of every other wave-form electrode, and the other scanning electrodes being also electrically connected together, so that the scanning electrodes are electrically connected in two corresponding sets each of which extends throughout the musical range of the instrument, and means for selectively polarising the two sets of scanning electrodes relative to the wave-form electrodes, whereby electrostatically generated frequencies corresponding to the pitches required throughout the musical range of the instrument may have their tone character simultaneously and uniformly varied.

3. An electrical musical instrument comprising a multiplicity of wave-form electrodes each having a wave form corresponding to a substantially complete series of harmonics, two scanning electrodes for each wave-form electrode, each of said two scanning electrodes comprising a set of transverse lines adapted to scan said waveform electrode, the lines of the two scanning electrodes being out of phase to the extent of 180 degrees, said wave-form electrodes and scanning electrodes forming a multiplicity of frequency generators corresponding to the tone pitches required throughout the range of the instrument, one scanning electrode of every wave-form electrode being electrically connected to one scanning electrode of every other wave-form electrode, and the other scanning electrodes being also electrically connected together, so that the scanning electrodes are electrically connected in two corresponding sets each of which extends throughout the musical range of the instrument, and means for selectively polarising the two sets of scanning electrodes relative to the wave-form electrodes, whereby electrostatically generated frequencies corresponding to the pitches required throughout the musical range .of the instrument may have their tone character simultaneously and. uniformly varied.

4. An electrical musical instrument comprising a multiplicity of wave-form electrodes each.

having a wave form corresponding to a substantially complete series oi harmonics, two scanning electrodes for each wave-form electrode, each of said two scanning electrodes comprising a set of transverse lines adapted to scan said wave-form electrode, the lines of the two scanning electrodes being. out of phase, said waveform electrodes and scanning electrodes forming a multiplicity of frequency generators corresponding to the tone pitchesrequired throughout the musical range of the instrument, one scanning electrode of every wave-form electrode being electrically connected to one scanning electrode of every other wave-form electrode, and the other scanning electrodes being also electrically connected together, so that the scanning electrodes are electrically connected in two corresponding sets each of which extends throughout the musical range of the instrument, and means for selectively polarising the two sets of scanning electrodes relative to the waveform electrodes, each through a complete range of potentials, whereby electro-statically generated frequencies corresponding to the pitches required throughout the musical range of the instrument may have their tone character simultaneously and uniformly varied.

5. An electrical musical instrument comprising a multiplicity of wave-form electrodes each having a wave form corresponding to a substantially complete series of harmonics, two scanning electrodes for each wave-form electrode, each of said two scanning electrodes comprising a set of transverse lines adapted to scan said wave-form electrode, the lines of the two scanning electrodes being out of phase to the extent of degrees, said wave-form electrodes and scanning electrodes forming a multiplicity of frequency generators corresponding to the tone pitches required throughout the musical range of the instrument, one scanning electrode of every wave-form electrode being electrically connected to one scanning electrode of every other wave-form electrode, and the other scanning electrodes being also electrically connected together, so that the scanning electrodes are electrically connected in two corresponding sets each of which extends throughout the musical range of the instrument, and means whereby one set only of said scanning electrodes may be polarised relative to said wave-form electrodes, whereby electrical impulses corresponding to the complete series of harmonics are adapted to be electrostatically generated throughout the musical range of the instrument, or both of said scanning electrodes may be polarised relative to said wave-form electrodes, whereby electrical impulses corresponding to only the odd harmonics are adapted to be generated electrostatically throughout the musical range.

6. An electrical musical instrument compris-. ing a multiplicity of wave-form electrodes, two scanning electrodes for each wave-form electrode, whereby a multiplicity of frequency generators are constituted corresponding to the tone pitches required throughout the range of the instrument, one scanning electrode of every wave-form electrode being electrically connected to one scanning electrode of every other waveform electrode, and the other scanning electrodes 8 being also electrically connected together, so REFERENCES CITED that the scanning electrodes are electrically -11, .6 u t connected in two corresponding sets each of g ifig ggg ig are OI lecold m the which extends throughout the musical range of the instrument, and means for selectively polar- UNITED STATES PATENTS ising the two sets of scanning electrodes rela- Number Name t tive to the Wave-form electrodes, whereby elec- 2 2 454 Hammond Aug 9 1933 trostatically generated frequencies c rr p 2,201,160 Curtis May 21, 1940 ing to the pitches required throughout the 2,276,390 Hanert Mar. 17, 1942 sical range of the instrument may have their tone it) "1 11"? character simultaneously and uniformly varied, EOIEIGN loud speaker means and electronic valves respec- Number Country Date tively individual to the wave-form electrodes for 501,520 Great Britain Feb. 28, 1939 controlling the transmission of said frequencies to said loud speaker means. 15

LESLIE EDWIN ALEXANDER BOURN. 

